how to fix the P0420 code on my Toyota RAV4 Fifth Generation (2019-present)

Solution

1. Preparation

• Gather necessary tools and parts.
• Ensure the vehicle is parked on a flat surface and the engine is cool.
• Disconnect the battery to prevent electrical shorts.

2. Inspect and Test O2 Sensors

• Tools Required: OBD-II scanner, multimeter
• Use the OBD-II scanner to check the live data from the O2 sensors while the engine is running.
• With the multimeter, measure the voltage output from the upstream O2 sensor. It should fluctuate between 0.1V and 0.9V.
• Check the downstream O2 sensor for a stable voltage reading; it should hover around 0.5V.

3. Inspect the Catalytic Converter

• Tools Required: Temperature probe, socket set
• Start the engine and let it reach operating temperature.
• Use the temperature probe to measure the exhaust temperature before the catalytic converter and compare it to the temperature after it.
• A significant temperature drop (more than 100°F) indicates a failing catalytic converter.

4. Replace O2 Sensors (if necessary)

• Tools Required: Socket set, torque wrench
• If the upstream or downstream O2 sensors are faulty, remove the old sensors using the socket set.
• Apply anti-seize compound on the threads of the new O2 sensors and install them, torquing to the manufacturer's specifications (typically around 30 ft-lbs).

5. Replace Catalytic Converter (if necessary)

• Tools Required: Socket set, exhaust hanger tool, torque wrench
• If the catalytic converter is confirmed faulty, disconnect the exhaust pipe from the exhaust manifold.
• Remove any exhaust hangers using the exhaust hanger tool.
• Install the new catalytic converter and secure it with new gaskets and bolts, torquing to the manufacturer’s specifications.

6. Reconnect Battery and Clear Codes

• Reconnect the battery.
• Use the OBD-II scanner to clear the P0420 code from the vehicle's memory.